Electric lamp having phosphor coating and heat deflector

ABSTRACT

In electric lamps which contain a gas filling at appreciable pressure and which have a phosphor coated on the inside of the envelope, it is necessary to guard against blowing phosphor off the wall by the jet of gas issuing from the exhaust tube at gas fill. Also in high intensity lamps, a heat deflector in the neck may be desirable to prevent overheating of the base. A heat deflector is provided in the form of a slotted disc which straddles the press and has tabs bent out therefrom at an acute angle. The tabs overlie the exhaust tube blow-out aperture in the stem and deflect the gas jet to prevent blowing phosphor off the wall at gas fill.

United States Patent [191 Anthony [i 3,783,322 [451 Jan. 1, 1974 ELECTRIC LAMP HAVING PHOSPIIOR COATING AND HEAT DEFLECTOR Inventor: John W. Anthony, Pepper Pike,

Ohio

Assignee: General Electric Company,

Schenectady, NY.

Filed: Dec. 14, 1972 Appl. N0.: 314,955

US. Cl 313/42, 313/43,}13/47,

313/109, 313/227, 313/229, 3l3/242 Int. Cl. H0lj 61/52 Field of Search 313/42, 43, 47

References Cited UNITED STATES PATENTS 10/1961 Edwards 313/42 Primary Examiner-Nathan Kaufman Assistant Examiner-Darwin R. l-lostetter Attorney-Ernest W. Legree et al.

[5 7] ABSTRACT In electric lamps which contain a gas filling at appreciable pressure and which have a phosphor coated on the inside of the envelope, it is necessary to guard against blowing phosphor off the wall by the jet of gas issuing from the exhaust tube at gas fill. Also in high intensity lamps, a heat deflector in the neck may be desirable to prevent overheating of the base. A heat deflector is provided in the form of a slotted disc which straddles the pressand has tabs bent out therefrom at an acute angle. The tabs overlie the exhaust tube blow-out aperture in the stem and deflect the gas jet to prevent blowing phosphor off the wall at gas fill.

5 Claims, 3 Drawing Figures BACKGROUND OF THE INVENTION The invention relates to electric lamps which have a phosphor coating on the inside of the envelope and whichhave an internal heat deflector or disc in the neck to prevent overheating of the base.

In gas tilled higher wattage electric lamps, it is customa ry to arrangea heat deflector element in the form of a disc in the neckiof the lamp envelope. The heat disc breaks up convection currents and reduces the radiant energy reachingthe base in order to prevent overheating of the base end of the lamp. The disc is usually supported by the stem or mount structure which comprises a r e-entrant glass stem tube extending into the bulb neck and having a pair of inlead wires extending therethrough and sealed in a flattened press portion at the inner end of the stem tube. In one such construction taught byU.S. Pat No. 2,624,019 Leighton, the stem press is formed with transverse grooves and the deflector disc is provided with a radial slot extending from its periphery and having upstanding flanges at its margins f tting in the grooves.

ln lamps which are coatedinternally with a phosphor, it isnecessary to guard against blowing the phosphor off the wall when the gas filling is introduced. Examples of such lamps are the so-called deluxe mercury lamps wherein an arc. discharge in high pressure mercury vapor takes place within a quartz arc tube located within an outer envelope or jacket coated internally with a phosphor. The phosphor converts some of the radiation from the arc tube, particularly longwave ultraviolet, to red radiation in order to improve the color rendition of the lamp. The outer envelope of this lamp is filled with an inactive gas, generally nitrogen, at a substantial fraction of an atmosphere.

a In the manufacture of the foregoing lamp, a completely processed arc tube is attached by support wires to the inleads of a mount to form a mount assembly. This assembly is then sealed into an outer envelope or jacket which has previously been coated internally with a phosphor in a binder. During the sealing operation, the envelope isheated sufficiently to decompose the binder, and gases and vapors resulting from such decomposition along with airare exhausted from the envelope. Theexhaust is performed through the exhuast tube of the mount which was previously blown open at the press for this purpose. Finally an inactive gas,'for instance nitrogen at a cold filling pressureof about 250 torr is released into the envelope through the exhaust tube which isthen tipped off. The foregoing operations are usually performed on a combined sealingexhausting machine. Since the binder has been driven out of the phosphontheelatter is relatively easily dislodged from the wall by the filling gas jet. The problem is aggravated by I increase in machine processing speed i which, by reducing the time interval for introduction of the filling gas, increases the force of the jet.

Prior to my invention, the only solution found to this problem has been to provide a amall deflecting disc in front of the blow-out aperture. This disc was attached to a support wire fastened by welding to the mount frame. The attachment of the deflecting disc was done manually in a relatively costly operation.

SUMMARY OF THE INVENTION In accordance. with .my invention, I have eliminated the jet deflector separately attached to themount and provide an improved heat reflector which is characterized by having a portion overlying the blow-out aperture in the mount and serving as a jet deflector.

In a preferred embodiment, the heat reflector or shield comprises a thin metal diskhaving a slotformed by a radial slit therein with narrow tabs on each sideof the slit bent at right angles and forming a collar straddling the press. The shieldhas in addition widertabs or ears bent out at an acute angle and overlyingthe blowout aperture in order to deflect thegas jet issuing therefrom at gas fill. Preferably a wider tab is provided on each side of the slotso that the blow-out aperture will be covered irrespective of the orientation of the heat disk on the stem. 1

DESCRIPTION OF DRAWING FIG. 1 is a sectioned side view of a high pressure metal vapor arc lamp embodying the invention in preferred form. r I

a FIG. 2 is an enlargedfragmentary side view of the neck end of the lamp envelope turned with respect to FIG. 1. i I

FIG. 3 is a plan view of the heat disc seen on line 3--3 in FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENT The invention may usefully be embodied in .a socalled deluxe mercury lamp shown in a 400-watt size in FIG. 1. The lamp 1 comprises an outer glass envelope or jacket 2 of ovoid shape having a neck 3 to the end of which is attached a screw-type base 4. The neck is closed by the usual re-entrant stem 5 having a press portion 6 through which are sealed a pair of inlead wires 7, 8 connected at their outer ends to the usual base terminals, namely the eyelet or center contact 9 and the base shell 11.

An inner arc tube 12 within the outer envelope is provided at opposite ends with a pair of main discharge supporting electrodes 13, 14 to which connects are rod 17. The side rod is welded to inlead 7 and extends to an anchoring dimple 18 at the dome end of the jacket which is engaged by a springy loop 19. The are tube is supported in the harness by clamping its flat ends between metal bands 21, 22 which are welded to single side rod 17.

In the illustrated lamp, arc tube 1.2 contains a charge of mercury and an inert gas such as argon at a pressure of about 20 millimeters of mercury. Alternatively, the

lamp may contain metal halides in addition to the mert cury charge, for instance sodium iodide and other metal halides. The inside of the outer envelope 2 is coated with a phosphor layer 23,.for instance yttrium vanadate, which converts longwave ultraviolet radiation produced by the mercury discharge into red radiation in order to improve the color rendition of the lamp.

In lamp making, the assembly of the stem 5, inlead wires 7, 8, side rod 17, and arc tube 12 with connections made to the inleads is known as the mount assembly. After outer envelope 2 has been coated internally with phosphor in a binder, the mount assembly is sealed into envelope 2 by heat fusing the flare of the stem to the neck as shown at 24 in FIG. 2, and cutting off the excess portion of the neck. This operation is usually done in a sealing-exhausting machine in which the outer envelope is heated to decompose the binder used to apply the phosphor. At the same time the envelope is exhausted of air, and any gases and vapors resulting from the decomposition of the binder, through a glass exhaust tube 25 which extends through the stem up to a blow-out aperture 26 which communicates with the interior of the outer envelope. Thereafter, at one of the last positions on the sealing exhaust machine, an inactive filling gas, suitably nitrogen at a cold filling pressure of 250 torr is released into the outer envelope through exhaust tube 25. It is the gas jet occurring at blow-out aperture 26 at this moment that may blow phosphor off the wall. The exhaust tube is then tipped off at 27.

In accordance with the invention, a heat reflector disc 28 is mounted on the stem in the neck of the outer envelope and serves both to prevent overheating of the base and to deflect the fill gas jet. The heat disc 28 is in the form of a stamping made of a suitable metal such as aluminum or bright plated iron, best seen in FIG. 3. The disc is mounted on the press portion 6 of the stem and for this purpose is provided with a radially extending slot 29 proportioned in width and depth to accommodate the stem press centrally therein. The press has shallow transverse grooves molded into opposite sides of the-flat portion at stem making. The grooves have a width (around five thirty-second inch in the particular case illustrated) appreciably greater than the thickness of the disc material. In order to support the disc transversely on the stem secure against tilting, it is formed with narrow tabs 30 which are bent at right angles to the plane of the disc and extend along the sides of the slot like a collar. The tabs 30 are of a height corresponding to the width of the grooves in the stem press wherein they are received with a snug sliding fit. In the center of the heat disc next to the narrow tabs, wider tabs or ears 31, semicircular in the illustration, are blanked out of the disc at an acute angle on the opposite side from the narrow tabs. The ears are so located that one, 31 in the drawing, will cover the blow-out aperture and deflect the jet caused by the inrush of filling gas.

To assemble the disc 28 on the stem of the lamp mount, it is merely necessary to slide collar tabs 30 of the disc into the grooves in the stem press until the disc is centered on the stem. The front ends of the collar tabs are then bent down at 32 to lock the disc in place. One of the downwardly bent ears, 31' as shown, will overlie blowout aperture 26 in the desired manner. By having two ears, one on each side of the slot, it is not necessary for the assembler to be concerned about orienting the heat disc on the stem and the blow-out aperture will be covered no matter on what side of the stem it occurs. Also it does occasionally happen in stem manufacture, at the time when the exhaust tube is heatfused to the stem tube to form the press and blown through beneath the press, that openings corresponding to the single opening 26 shown, are blown out on both sides. However this creates no difficulty with the preferred form of heat disc illustrated. Since it has ears on both sides of the slot, it 'will effectively cover both apertures.

What I claim as new and desire to secure by Letters Patent of the United States is:

I. An electric lamp comprising a sealed vitreous envelope having a generally tubular neck portion,

a re-entrant stem tube extending axially into said neck portion and terminating in a press at its inner end,

a source of radiant energy within said envelope,

a phosphor coating on the inside of said envelope,

an exhaust tube extending into said stem tube and terminating in a blow-out aperture,

a gas filling within said envelope,

and a heat shield comprising a thin metal piece transversely mounted on said stem and partitioning off the outer end of the neck, said shield having a ra dial slot therein straddling the press,

said shield having a tab bent out therefrom at an acute angle and overlying the blow-out aperture in order to deflect the gas jet issuing therefrom at gas fill of said envelope and prevent blow-off of phosphor from the envelope wall.

2. A lamp as in claim 1 wherein said heat shield has two tabs bent out therefrom at an acute angle, one on each side of the slot, so that one tab will overlie the blow-out aperture irrespectively of the orientation of the shield on the stem.

3. An electric lamp comprising a sealed vitreous envelope having a generally tubular neck portion and a base attached thereto,

a re-entrant stem tube extending axially into said neck portion and terminating in a press at its inner end,

inlead wires sealed through said press and extending into said envelope, the outer ends of said inleads being connected to said base,

a source of radiant energy within said envelope connected across said inleads,

a phosphor coating on the inside of said envelope,

an exhaust tube extending into said stem tube and terminating in a blow-out aperture on at least one side of said press,

a gas filling at appreciable pressure within said envelope,

and a heat shield comprising a thin metal disc transversely mounted on said stem and partitioning off the outer end of the neck, said disc having a slot formed by a radial slit therein and narrow tabs on each side of the slit bent at right angles to form a collar accommodating the press,

said disc having at least one ear bent out therefrom at an acute angle and overlying the blow-out aperture in order to deflect the gas jet issuing therefrom at gas fill of said envelope and prevent blow-off of phosphor from the envelope wall.

4. A lamp as in claim 3 wherein said disc has two ears bent out therefrom at an acute angle, one on each side of the slot, so that one ear will overlie the blow-out aperture irrespectively of the orientation of the shield on the stem.

5. A lamp as in claim 3 wherein the narrow tabs on each side of the press are bent down towards each other at the front end of the slot in order to lock the disc on the stem. 

1. An electric lamp comprising a sealed vitreous envelope having a generally tubular neck portion, a re-entrant stem tube extending axially into said neck portion and terminating in a press at its inner end, a source of radiant energy within said envelope, a phosphor coating on the inside of said envelope, an exhaust tube extending into said stem tube and terminating in a blow-out aperture, a gas filling within said envelope, and a heat shield comprising a thin metal piece transversely mounted on said stem and partitioning off the outer end of the neck, said shield having a radial slot therein straddling the press, said shield having a tab bent out therefrom at an acute angle and overlying the blow-out aperture in order to deflect the gas jet issuing therefrom at gas fill of said envelope and prevent blow-off of phosphor from the envelope wall.
 2. A lamp as in claim 1 wherein said heat shield has two tabs bent out therefrom at an acute angle, one on each side of the slot, so that one tab will overlie the blow-out aperture irrespectively of the orientation of the shield on the stem.
 3. An electric lamp comprising a sealed vitreous envelope having a generally tubular neck portion and a base attached thereto, a re-entrant stem tube extending axially into said neck portion and terminating in a press at its inner end, inlead wires sealed through said press and extending into said envelope, the outer ends of said inleads being connected to said base, a source of radiant energy within said envelope connected across said inleads, a phosphor coating on the inside of said envelope, an exhaust tube extending into said stem tube and terminating in a blow-out aperture on at least one side of said press, a gas filling at appreciable pressure within said envelope, and a heat shield comprising a thin metal disc transversely mounted on said stem and partitioning off the outer end of the neck, said disc having a slot formed by a radial slit therein and narrow tabs on each side of the slit bent at right angles to form a collar accommodating the press, said disc having at least one ear bent out therefrom at an acute angle and overlying the blow-out aperture in order to deflect the gas jet issuing therefrom at gas fill of said envelope and prevent blow-off of phosphor from the envelope wall.
 4. A lamp as in claim 3 wherein said disc has two ears bent out therefrom at an acute angle, one on each side of the slot, so that one ear will overlie the blow-out aperture irrespectively of the orientation of the shield on the stem.
 5. A lamp as in claim 3 wherein the narrow tabs on each side of the press are bent down towards each other at the front end of the slot in order to lock the disc on the stem. 